Lice live approximately 30 days on a human scalp. An adult female can lay 6-8 nits (lice eggs) per day. These are attatched to the hair shaft, close to the scalp with a very strong glue. A nit must have the warmth from the scalp in order to develop and hatch. Immediately after hatching, the nymph (infant louse) must have human blood. It takes approximately 9 days for a nit to hatch and another 7-9 days for a nymph to become an adult.

Lice are unable to jump or fly and they are unable to live on pets. Lice use their 6 legs to crawl and move very fast in the hair. They are able to crawl on other surfaces but are not as speedy as they are in the hair. A well fed adult louse may live off of a host scalp for 24-48 hours. A nit or nymph cannot survive off of a host. Lice are able to close their breathing tube and hold their breath for hours when wet , so it can be difficult to drown and smother them.

Lice hold on to hair using claw like appendages. In North America, they are adapted to hold on to round, thin, hair shafts very tightly, but they are able to live on oval, thick hair shafts.

When hatched, a nymph appears to be a translucent gray, but becomes more tan/brown after it feeds. An adult louse will appear to be gray, tan or brown.

These images are used with permission from Headlice.org.

​Checking for lice on the scalp

Pick a work area with bright light or go outside, if possible. Part the hair in sections, starting at the nape of the neck and moving up around the ears. These areas are considered "hot spots" for lice and nits. Check for tiny, oval, whitish eggs (nits) attached close to the scalp. ​​

A nit is not easily removed and must be pulled down the hair shaft to get it off of the hair. If something is visible that can be easily picked up, it is lint, hair products or scalp skin flakes. It is not a nit.

Using a flashlight may be helpful in identifying lice and nits. Lice do not like light and will move away. This quick movement will sometimes give away the presence of lice. Lice are more active at night and can interrupt the sleep of the host. An itchy scalp can be present but not everyone reacts to the saliva released while a louse feeds. A red itchy rash can be present on the scalp or neck, typically caused by scratching.